A better understanding of users’ decision making processes gives service providers greater insight to fac- tors that guide users’ adoption of new services and the development of future services. In this study, we assumed that key determinants of behavioral intentions to use mobile communication services including multimedia messaging services are the psychological traits of users and social factors. This research adhered to the social cognitive and social influence perspectives that are widely accepted theories of indi- vidual behavior to explore the multimedia messaging services usage behavior. An empirical investigation of current multimedia messaging services users in South Korea was conducted. The partial least squares analysis exhibited strong support for the role of credibility of the service, relative advantages, and per- ceived ease of use in shaping users’ attitude and intention to use multimedia messaging services. This research accounted for the key forces of technological service characteristics and personal psychological traits affecting users’ intention to adopt multimedia messaging services. This empirical analysis showed that the psychological traits of self-efficacy and peer influence are the most important factors to the formation of intention to use the new mobile service.